Alfred Adler is a famous psychologic and psychopatholic theorist. Adler is perhaps best known for his theory on dream interpretations and his ideas on human nature and psychology in general. Today, many of his findings are still incorporated into psychiatric care and play a large role in college courses following the subject. In many cases, Adler is more important to psychology than Freud. Read some Alfred Adler famous quotes below.

It is easier to fight for one's principles than to live up to them.
Alfred Adler: Apostle of Freedom (1939), ch. 5
The life of man is the life of a moving being, and it would not be sufficient for him to develop body alone. A plant is rooted: it stays in one place and cannot move. It would be very surprising, therefore, to discover that a plant had a mind; or at least a mind in any sense which we could comprehend. If a plant could foresee or project consequences, the faculty would be useless to it. What advantage would it be for the plant to think: 'Here is someone coming. In a minute he will tread on me, and I shall be dead underfoot'? The plant would still be unable to move out of the way. All moving beings, however, can foresee and reckon up the direction in which to move; and this fact makes it necessary to postulate that they have minds or souls.The truth is often a terrible weapon of aggression. It is possible to lie, even to murder, for the truth.

The striving for significance, this sense of yearning, always points out to us that all psychological phenomena contain a movement that starts from a feeling of inferiority and reach upward. The theory of Individual Psychology of psychological compensation states that the stronger the feeling of inferiority, the higher the goal for personal power.
Progress in Individual Psychology (1923)
To be human means to feel inferior.
Contemporary Theories and Systems in Psychology (1960)
Meanings are not determined by situations, but we determine ourselves by the meanings we give to situations.
What Life Should Mean to You (1937), p. 14
Man knows much more than he understands.
A Primer of Adlerian Psychology : The Analytic-Behavioural-Cognitive Psychology of Alfred Adler (1999)